In this article, we have designed and simulated a 64 channels dense wavelength division multiplexed passive optical network (DWDM PON) with 100 GHz channel spacing and an overall transmission capacity of 640 Gb/s. There are 32 downstream and 32 upstream channels. Each channel is modulated at a data rate of 10 Gb/s constituting a total of 640 Gb/s system. Phenomenon of dispersion, attenuation, self and cross phase modulations are incorporated in the system design to observe noise effect on the transmitted signal. Channel length is varied to check maximum transmission reach and its effect on signal performance parameters that is, Q‐factor, bit error rate, eye amplitude, optical signal to noise ratio, extinction ratio, and peak to peak jitter are recorded. It is noted that our DWDM PON successfully transmitted 640 Gb/s data bi‐directionally over a transmission distance of 150 km.